A lithium ion secondary battery attracts attention as a power source of a portable device or a power source of an electric vehicle, a hybrid electric vehicle, or the like. A currently prevailing lithium ion secondary battery is one that has a positive active material comprising LiMO2 (M represents Co, Ni, Mn, V, Al, Mg, or the like), a negative active material comprising graphite, and a nonaqueous electrolyte comprising Li salt and a nonaqueous solvent. Such a lithium ion secondary battery shows a high discharge voltage and has a high output as the advantages.
Such a lithium ion secondary battery is disclosed in, for example, JP2005-336000A, JP2003-100300A, and JP2003-59489A.